Horse Power was comparison everyone could understand.
Suddenly, Watt had put the steam engine into a language that made sense to the layman. Which is exactly what Steve Jobs did when he launched the iPod.
He didn’t compare it to to other MP3 players for speed and fidelity.
That would have been a market-share comparison.
Steve Jobs had a much bigger opportunity in mind, market-growth.
That’s why he compared the iPod to something ordinary people could understand.
He simply held it up and said “A thousand songs in your pocket.”
Because 200 years later the rules for creative communication haven’t changed. You talk to the audience in their language. Not yours.